Pension And Other Postretirement Benefits (Reconciliation Of Fair Value Measurements Using Significant Unobservable Inputs) (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
Dec. 31, 2012	Dec. 31, 2011
Fair value of plan assets at end of year	$ 2,360	$ 1,975
Significant Unobservable Inputs (Level 3) [Member]
Fair value of plan assets at beginning of year	165	150
Transfer in (out) of Level 3	2
Purchases	15	22
Sales	(5)	(6)
Settlements	(13)	(10)
Unrealized gain/(loss)	1	4
Realized gain/(loss)	9	5
Fair value of plan assets at end of year	174	165
Equity Securities [Member] \| Significant Unobservable Inputs (Level 3) [Member]
Fair value of plan assets at beginning of year	27	30
Transfer in (out) of Level 3
Purchases	4	2
Sales	(4)	(5)
Settlements	(1)
Unrealized gain/(loss)	4	(1)
Realized gain/(loss)	1	1
Fair value of plan assets at end of year	31	27
Fixed Income [Member] \| Significant Unobservable Inputs (Level 3) [Member]
Fair value of plan assets at beginning of year	9	3
Transfer in (out) of Level 3	2
Purchases	2
Sales	(1)	(1)
Settlements	1	7
Unrealized gain/(loss)
Realized gain/(loss)
Fair value of plan assets at end of year	13	9
Private Equity [Member] \| Significant Unobservable Inputs (Level 3) [Member]
Fair value of plan assets at beginning of year	64	62
Transfer in (out) of Level 3
Purchases	4	11
Sales
Settlements	(8)	(11)
Unrealized gain/(loss)	(11)	(4)
Realized gain/(loss)	7	6
Fair value of plan assets at end of year	56	64
Real Estate [Member] \| Significant Unobservable Inputs (Level 3) [Member]
Fair value of plan assets at beginning of year	65	55
Transfer in (out) of Level 3
Purchases	5	9
Sales
Settlements	(5)	(6)
Unrealized gain/(loss)	8	9
Realized gain/(loss)	1	(2)
Fair value of plan assets at end of year	$ 74	$ 65

Assets, usually stocks, bonds, and other investments, that have been segregated and restricted (usually in a trust) to provide benefits, at their fair value as of the measurement date. Plan assets include amounts contributed by the employer (and by employees for a contributory plan) and amounts earned from investing the contributions, less benefits paid. If a plan has liabilities other than for benefits, those non-benefit obligations may be considered as reductions of plan assets.

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The amount that relates to an irrevocable action that relieves the employer (or the plan) of primary responsibility for a benefit obligation and eliminates significant risks related to the obligation and the assets used to effect the settlement. Examples of transactions that constitute a settlement include (a) making lump-sum cash payments to plan participants in exchange for their rights to receive specified benefits and (b) purchasing nonparticipating annuity contracts.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 132R

-Paragraph 5

-Subparagraph b

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

-SubTopic 30

-Section 15

-Paragraph 6

-Subparagraph (a)(1)

-URI http://asc.fasb.org/extlink&oid=7577095&loc=d3e8001-114927

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 87

-Paragraph 264

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 88

-Paragraph 3

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 5: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 106

-Paragraph 518

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 6: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 132R

-Paragraph 5

-Subparagraph d(iv)(b)(i)

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 7: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

-SubTopic 20

-Section 50

-Paragraph 1

-Subparagraph (b)(8)

-URI http://asc.fasb.org/extlink&oid=21915506&loc=d3e1928-114920

+ Details